Prepare for battle, soldier! Your tour of duty begins NOW! We are under siege and the responsibility of commanding the heavy artillery XG500 surface-to-air cannon falls in your seasoned shoulders. The task will be anything but easy; attack choppers, jets and Rangers will do their best to destroy our base. Under no circumstances can you allow three enemy troops into the perimeter or sustain a direct high from a deadly bunker buster. The odds are against us, but your skills are great. Are you up for the challenge? Dare test your mettle? Rules: Shoot at everything. If 3 troopers infiltrate your defenses, game over. If you get hit by a bunker buster, game over.